1. Field of the Invention
The present invention relates to a fuel composition comprising a high softening point hydrocarbon in a water colloidal dispersion, and a method for making it.
2. Description of the Related Art
There are several patents describing the emulsification of viscous petroleum hydrocarbons in water. The main purpose is to reduce viscosity so that the petroleum hydrocarbon can be converted into a liquid form which is easier to transport and convert to power or chemical feedstocks. Using abundant water as one of the ingredients in preparing these dispersions makes these emulsification processes very attractive. Predominantly nonionic or anionic surfactant packages have been used and in some cases cationic surfactants have been used. The surfactant solution in water and the heated petroleum hydrocarbon are brought in contact and subjected to shearing action using a suitable mixing device. Various mixing devices have been used such as simple blenders, gear pumps, colloidal mills, static mixers, and dynamic mixers. Most of the patents describe emulsification of hydrocarbons at ambient pressures. The petroleum hydrocarbons used in these processes include vacuum residues, atmospheric residues, crude oils, etc. The following is a list of examples of such patents:
U.S. Pat. No. 5,411,558 PA0 U.S. Pat. No. 5,399,293 PA0 U.S. Pat. No. 5,024,676 PA0 U.S. Pat. No. 5,000,872 PA0 U.S. Pat. No. 5,000,757 PA0 U.S. Pat. No. 4,978,365 PA0 U.S. Pat. No. 4,923,483 PA0 U.S. Pat. No. 4,793,826 PA0 U.S. Pat. No. 4,666,457 PA0 U.S. Pat. No. 4,618,348 PA0 U.S. Pat. No. 4,265,264 PA0 U.S. Pat. No. 4,776,977 PA0 U.S. Pat. No. 3,997,398 PA0 U.S. Pat. No. 3,630,953 PA0 U.S. Pat. No. 3,519,006 PA0 U.S. Pat. No. 3,497,371 PA0 U.S. Pat. No. 4,943,390 PA0 U.S. Pat. No. 4,832,747 PA0 U.S. Pat. No. 4,821,757 PA0 EP 0732376A2
There are a few patents describing emulsification under higher temperatures and pressures. If the hydrocarbon is too viscous it has to be heated to a certain temperature which results in the temperature of the mix consisting of surfactant solution and the petroleum hydrocarbon to be much higher than the boiling point of water. When the temperature of formation of the emulsion is higher than the boiling point of water the system needs to be at higher pressures to prevent water from boiling off and cooling systems are necessary to cool the emulsions below the boiling point of water before the pressures can be released. The examples in these patents indicate that the hardest material that has been emulsified had a softening point of about 50.degree. C. and in another example had a viscosity of 1000 centipoise ("cps") at 100.degree. C. When hydrocarbons having a softening point above 50.degree. C. were used they were either diluted with fluxant oils, softened with solvent, or were powdered and made into a slurry with softer hydrocarbon emulsions. The following is a list of examples of such patents:
Hydrocarbons above a softening point of about 95.degree. C. have not been emulsified by using methods described in the prior art, nor used as a fuel in the form of an emulsion. There is a need for preparing dispersions with hydrocarbons with high softening points in water containing as high a percentage of dispersed hydrocarbon phase as possible. Hard hydrocarbons have been ground into fine powders and dispersed in water as a slurry. These hard hydrocarbon slurries have certain basic differences when compared to an emulsified hydrocarbon in water. Hard hydrocarbon slurries consist of non-spherical ground particles having median particle sizes of about 18 to 32 microns which are several fold higher compared to a hydrocarbon emulsion in water whose particles sizes are less than about 5 microns. Hard hydrocarbon slurries have a higher rate of settlement and much higher viscosity compared to emulsified hydrocarbon dispersions. Moreover, since hard hydrocarbons do not flow, they cannot be characterized in terms of softening point temperatures. The equipment that is needed to make these fine powders and slurries is expensive compared to emulsification equipment. Such hydrocarbons include bottom products obtained from the solvent deasphalting process such as the residual oil solvent extraction process, commonly referred to as the "ROSE" process for recovering various asphaltic materials.
Stringent environmental regulations have created a need for cleaner transportation fuel and a reduction in the use of high sulfur fuel oil. Crude oil is also becoming progressively heavier (lower in API gravity) and higher in sulfur content. The ROSE process upgrades resids by separating the heavy fraction from the lighter fraction using a variety of solvents. A number of feedstocks can be processed through a ROSE unit such as vacuum resid, atmospheric resid, tar sand and other heavy bitumen. The ROSE process produces deasphalted oil and asphaltenes. The deasphalted oil can be used for a variety of purposes. The asphaltenes have a softening point between about 60.degree. C. to about 200.degree. C. The asphaltenes obtained from the deasphalting process are difficult to handle and pump because of their high viscosity and high softening point. The higher softening point also prevents the asphaltenes from being used for road paving purposes without blending with other softer materials. In order to handle and transport asphaltenes a reduction in viscosity is required. One possible solution is to make a liquid form of asphaltenes by preparing a colloidal dispersion of asphaltenes in water which are storage stable, stable towards transportation and stable towards pumping so that the asphaltenes can be used in various applications including use as a liquid fuel.
There appear to be no examples of colloidal dispersions of hydrocarbon materials with a softening point above about 90.degree. C. The above mentioned higher softening point materials have not been previously made into emulsions or used in emulsified form as hydrocarbon fuels.